Bar button item on every view with specific controller function - swift

Question

I have to display a navigation bar button item on almost every view in the project.
I extended UIViewController
extension UIViewController{
func addNavBarItem(){
//add the bar button item
}
}
And I call addNavBarItem() on the viewDidLoad. However, the action taken when this button is tapped can be different for each view. Is there a way to set the target for this button to the actual view controller that called this method? Ideally I would want something like....
extension UIViewController{
func addNavBarItem(){
//do stuff
btn.addTarget(self, action: #selector(OriginalViewController.doSomething), forControlEvents: .TouchUpInside)
}
}
But OriginalViewController isn't available. Is there a quick solution or alternative pattern I should employ?

Answer 1

One solution that I use is to subclass UINavigationController and put my navigation bar item code in to the willShowViewController delegate method like so...
class MyNavigationController : UINavigationController {
override func navigationController(navigationController: UINavigationController, willShowViewController viewController: UIViewController, animated: Bool) {
super.navigationController(navigationController, willShowViewController: viewController, animated: animated)
let backButton = UIBarButtonItem(image: UIImage(named: "ic_menu"), style: UIBarButtonItemStyle.Plain, target: viewController, action: "doSomething")
viewController.navigationItem.leftBarButtonItem = backButton
}
}
This means when you add the target you can reference the exact viewController that is being shown by the navigation controller.